I'm not even sure what sustained speed is actually. I look around and some people say that 40mb/s is what they are getting on their drives, for sustained speed, and that was just the first thing I clicked in google. The jumper should be out though, all open.

Maybe new chipset drivers are needed, I dunno. You could download SyTools, from sygate, if you have a few hours to kill, scan your drive with it and if it gives errors, you can RMA the thing, and try out a new one, I hate RMAing things though. I had to RMA the first 250Gb Barracuda I got, weird problems with it.